The most familiar form of equipment found in the art of mixing fluids and solids can best be described as that of the "stirred" vessel; i.e., a tank or mixing chamber having one or more mechanically driven agitators or impellers mounted therein. Said agitators can vary widely in type, location and method of mounting in a particular mixing chamber. However, the main mixing chamber in such equipment has most often been fabricated with a generally cylindrical shape. Stationary wall baffles are frequently mounted on the inside lateral surfaces of such cylindrical mixing chambers in order to modify the flow patterns created by the mechanically driven agitators employed therein, especially when said agitators are designed to rotate concentrically around the central axis of said cylindrical chambers.
Basic teachings regarding the effectiveness of various types and sizes of agitators and baffle systems and how they tend to interact to achieve efficient mixing are available in technical literature such as the article by E. J. Lyons in Chemical Engineering Progress 44, p. 341 et seq (1948). An important recent advance in the art of improving the performances of various types of agitators by using them with a unique system of wall baffles is disclosed in U.S. Pat. No. 4,941,752. The integrated apparatus described in this patent has proved to be especially useful in mixing and reacting pulped fibrous solids with a wide variety of fluid reagents.